E-block having improved resonance characteristics and improved fragility

ABSTRACT

An improved E-block for positioning one or more transducer assemblies proximate one or more rotating storage disks of a disk drive is provided herein. The E-block includes an actuator hub and one or more actuator arms which cantilever away from the actuator hub for holding the transducer assemblies proximate the rotating storage disks. As provided herein, at least one of the actuator arms is a depopulated actuator arm which retains less than two transducer assemblies. Each depopulated actuator arm includes at least one, weighted segment integrally formed into the depopulated actuator arm. Further, each depopulated actuator arm has an arm thickness which is less than an arm thickness for a double head actuator arm. The weighted segment and the reduced arm thickness allow the depopulated actuator arm(s) to vibrate similar to a populated actuator arm(s). This allows the disk drive to be designed and tuned to improve fragility and resonance characteristics of the E-block.

FIELD OF THE INVENTION

The present invention relates generally to disk drives for storing data.More specifically, the present invention relates to an E-block havingone or more actuator arms which include one or more integrally formedweighted segments to improve the resonance characteristics and thefragility of the E-block.

BACKGROUND

Disk drives are widely used in computers and data processing systems forstoring information in digital form. These disk drives commonly use oneor more rotating storage disks to store data in digital form. Eachstorage disk typically includes a data storage surface on each side ofthe storage disk. These storage surfaces are divided into a plurality ofnarrow, annular, regions of different radii, commonly referred to as“tracks”. Typically, an E-block having one or more actuator arms is usedto position a data transducer of a transducer assembly proximate eachdata storage surface of each storage disk. The E-block is moved relativeto the storage disks with an actuator motor. Depending upon the designof the disk drive, each actuator arm can retain none or two transducerassemblies.

The accurate and stable positioning of each transducer assembly neareach data storage surface is critical to the transfer and retrieval ofinformation from the disks. As a result thereof, vibration in theE-block and the transducer assembly can cause errors in data transfersdue to inaccuracies in the positioning of the data transducers relativeto the storage disks. This is commonly referred to as “off-trackmotion”. Additionally, extreme shock loads during shipping, handling,and/or installation of the disk drive can cause extreme vibration in theE-block and the transducer assemblies. The extreme vibration can causethe data transducers to overcome the suspension load force and leave thedisk surface, resulting in a “slap” or “crash” when returning to thestorage disk surface.

Because it is most economical to utilize all surfaces of the disks in adisk drive, the E-block which has the heads attached at the ends of eachof its arms results in an asymmetry of the top and bottom arms withrespect to the inner arms. The outer actuator arms retaining only onehead are referred to as being “depopulated”. The inner actuator armsretaining two transducer assemblies are referred to as being“populated”. The depopulated actuator arms bend and flex at differentfrequencies than the populated actuator arms as a result of theasymmetrical nature of having only one transducer assembly coupled tothe actuator arm. The result of this asymmetry is additional vibrationmodes and “off track” motion.

FIG. 1A is a top plan view which illustrates the vibration in a priorart E-block 10P and transducer assemblies 12P with force applied by anactuator motor (not shown). FIG. 1B is a side perspective view whichalso illustrates the vibration in the prior art E-block 10P and thetransducer assemblies 12P with force applied by an actuator motor (notshown). The prior art E-block 10P in FIGS. 1A and 1B includes fouractuator arms 14P and six transducer assemblies 12P. The upper most andlower most actuator arms 14P are depopulated while the middle twoactuator arms 14P are populated. As a result of the asymmetrical design,the actuator arms 14P and the transducer assemblies 12P each reactdifferently to force applied by the actuator motor and to shock loads tothe disk drive.

FIGS. 2A-2C further highlight how the asymmetrical design effect theresonance characteristics of the actuator arms and/or the transducers.For example, FIG. 2A illustrates a computer simulation of the off trackmotion for each data transducer 16P after force applied by the actuatormotor for the E-block illustrated in FIGS. 1A and 1B. FIG. 2Billustrates a computer simulation of the G's to unload as a function ofshock duration for the E-block illustrated in FIGS. 1A and 1B. Statedanother way, FIG. 2B illustrates the G's required to lift the transduceraway from the surface of the storage disk for a given shock duration. InFIG. 2B, the curve designated 18P illustrates the movement of thetransducer on the depopulated actuator arm while the curves designed 20Peach illustrate movement of the transducer for a populated actuator arm.FIG. 2C illustrates the amount of arm deflection for the actuator arms14P of the E-block 10P as a function of shock duration for the E-blockillustrated in FIGS. 1A and 1B. More specifically, in FIG. 2C, curvedesignated 22P represents the movement of the actuator arm which doesnot include any transducer assemblies, curve designated 24P representsthe movement of the actuator arm with a single transducer assembly, andcurve designated 26P represents the movement of the actuator arm havingtwo transducer assemblies attached to the actuator arm.

One attempt to eliminate the effect of the depopulated actuator armsincludes attaching a transducer assembly to each side of each actuatorarm so that each arm is populated and adding an additional storage diskto the disk drive. However, the two additional transducer assemblies andthe additional storage disk increase the cost for the disk drive andtake up valuable space in the disk drive. Alternately, to maintainsymmetry of the E-block, a three arm E-block with six transducers couldbe used in place of the four arm E-block. With this design, one extradisk would be required and two surfaces, the outermost surface on theoutermost disks, would not be utilized.

Another attempt to minimize off track vibration and head slap includescantilevering a mass in the form of a dummy swage plate from eachdepopulated actuator arm. The dummy swage plate can be effective inadding the additional mass to the system. However, the dummy swage plateincreases the inertia of the E-block. This results in increased dataseek times for the disk drive because the actuator motor is not able tomove the E-block as quickly. Further, the dummy swage plate typicallyhas different dynamic behavior and stiffness since it is not practicalto make one the full transducer assembly length. Typically, short,simple shaped cantilever beams or swage bases are used. Additionally,the dummy swage plate is somewhat difficult to properly position andattach to the depopulated actuator arm. This adds extra components tothe disk drive and increases the manufacturing cost of the disk drive.

Yet another attempt to minimize vibration effecting head slap includesusing resilient mounts to secure the disk drive. The resilient mountsflex to attenuate shock and reduce head slap. Unfortunately, theresilient mounts also reduce disk drive performance during a data seekrequest.

In light of the above, it is an object of the present invention toprovide a stable E-block having one or more depopulated actuator armsfor a disk drive and method for making the same. Another object of thepresent invention is to provide an E-block having improved vibration andresonance characteristics, which does not degradate the performance ofthe disk drive. Still another object of the present invention is toprovide an E-block which minimizes head slap and reduces drive fragilityto shipping, handling, and installation. Yet another object of thepresent invention is to provide an E-block which can be adapted to beused with disk drives having an alternate number of storage disks. Stillanother object of the present invention is to provide an E-block havingone or more depopulated actuator arms which is relatively easy andinexpensive to manufacture.

SUMMARY

The present invention is directed to an E-block and a method formanufacturing an E-block for a disk drive which satisfies theseobjectives. The E-block includes an actuator hub and a depopulatedactuator arm secured to the actuator hub. The depopulated actuator armretains less than two transducer assemblies. Uniquely, the depopulatedactuator arm includes a first weighted segment integrally formed intothe depopulated actuator arm. The first weighted segment is sized,shaped and located to improve the resonance characteristics of thedepopulated actuator arm.

The improved resonance characteristics reduce the amount of vibration inthe E-block and the transducer assemblies, thereby decreasing off-trackmotion, minimizing head slap, and increasing the accuracy of the diskdrive. Moreover, because the weighted segment is an integral part of theactuator arm and does not cantilever away from the actuator arm, theperformance impact to the actuator motor is minimized and the cost formanufacturing the E-block is not increased.

In one embodiment, the depopulated actuator arm is a single headactuator arm which retains a single transducer assembly. The single headactuator arm includes a coupled side and an opposed uncoupled side. Thesingle head actuator arm secures one transducer assembly to the coupledside, near one storage disk. In this embodiment, the weighted segment ispreferably sized, shaped and located to counterbalance the singletransducer assembly.

In another embodiment, the depopulated actuator arm is a no headactuator arm which retains no transducer assemblies. The no headactuator arm including a pair of spaced apart uncoupled sides and a pairof spaced apart weighted segments. Each weighted segment is integrallyformed into the actuator arm and is sized, shaped and positioned toimprove the resonance characteristics of the no head actuator arm.

Depending upon the design of the disk drive, the E-block can include oneor more single head actuator arms, one or more no head actuator arms andone or more double head actuator arms. As provided in detail below, thisfeature, for example, allows the same E-block design to be alternatelymanufactured for disk drives having different numbers of storage disks.

The present invention is also a method for manufacturing an E-block fora disk drive. The method includes the steps of forming an E-block havingan actuator hub and a depopulated actuator arm secured to the actuatorhub. The depopulated actuator arm includes an uncoupled side and aweighted segment integrally formed into the depopulated actuator arm.The weighted segment is sized, shaped and located to improve theresonance characteristics of the depopulated actuator arm.

Additionally, the arm thickness of each depopulated actuator arm is lessthan the arm thickness of each double head actuator arm. This causes thelateral stiffness of each depopulated actuator arm to be less than thelateral stiffness of each double head actuator arm. The combination ofthe weighted segment and reduced lateral stiffness allows eachdepopulation actuator arm to have approximately the same resonancecharacteristics as each double head actuator arm.

Importantly, the integrally formed weighted segment and reduced lateralstiffness improves the resonance characteristics of the E-block withoutsignificantly increasing the cost of manufacturing or degrading theperformance of the disk drive. With the design provided herein, thedepopulated actuator arms and the double head actuator arms havesubstantially similar resonance characteristics. This allows the diskdrive manufacturer to better design and tune the disk drive to minimizehead slap and off-track motion. Further, the disk drive can be bettertuned to improve the fragility of the disk drive to shock loads duringshipping and handling.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of this invention, as well as the invention itself,both as to its structure and its operation, will be best understood fromthe accompanying drawings, taken in conjunction with the accompanyingdescription, in which similar reference characters refer to similarparts, and in which:

FIG. 1A is a top view illustration flexing in a prior art E-block andtransducer assemblies;

FIG. 1B is a perspective view illustrating flexing in a prior artE-block and transducer assemblies;

FIG. 2A illustrates a computer simulation of the bode plots for theprior art E-block and transducer assemblies of FIGS. 1A and 1B;

FIG. 2B illustrates a computer simulation of the G's to unload thetransducers from the storage disk as a function of shock duration forthe prior art E-block and transducer assemblies of FIGS. 1A and 1B;

FIG. 2C illustrates a computer simulation of the arm deflection of theactuator arms in FIGS. 1A and 1B;

FIG. 3 is a perspective view of a disk drive having features of thepresent invention;

FIG. 4 is a perspective view of a first embodiment of an E-block,transducer assemblies, coil and flex circuit having features of thepresent invention;

FIG. 5 is a side plan view of the E-block, transducer assemblies andcoil illustrated in FIG. 4;

FIG. 6 is a perspective view of a second embodiment of an E-block,transducer assemblies, coil and flex circuit having features of thepresent invention;

FIG. 7 is a side plan view of the E-block, transducer assemblies andcoil illustrated in FIG. 6;

FIG. 8 is a perspective view of a third embodiment of an E-block,transducer assemblies, coil and flex circuit having features of thepresent invention;

FIG. 9 is a side plan view of the E-block, transducer assemblies andcoil illustrated in FIG. 8;

FIG. 10 illustrates a computer simulation of the resonance curves forthe data transducers illustrated in FIGS. 8 and 9 after movement;

FIG. 11 illustrates a computer simulation of the G's to unload thetransducers from the storage disk as a function of shock duration forthe embodiment illustrated in FIGS. 8 and 9; and

FIG. 12 illustrates a computer simulation of the arm deflection of theactuator arms as a function of shock duration for the E-blockillustrated in FIGS. 8 and 9.

DESCRIPTION

Referring initially to FIG. 3, a disk drive 10 according to the presentinvention includes (i) a drive housing 12, (ii) a disk assembly 14,(iii) an E-block 16 having one or more actuator arms 18, (iv) one ormore transducer assemblies 20, and (v) an actuator motor 22. The E-block16 provided herein has improved resonance characteristics. This reducesmovement and flexing in the actuator arms 18 and allows the E-block 16to accurately position the transducer assemblies 20 for more accuratedata transfers. Additionally, the E-block 16 can be better tuned toreduce drive fragility to shipping, handling, and installation.

As an overview, the E-block 16 is uniquely designed so that the actuatorarms 18, with the transducer assemblies secured thereto, each havesimilar resonance characteristics. This allows a drive manufacturer (notshown) to design and tune the disk drive 10 to minimize head slap andoff-track motion.

A detailed description of the various components of a disk drive 10 isprovided in U.S. Pat. No. 5,208,712, issued to Hatch et al. The contentsof U.S. Pat. No. 5,208,712 are incorporated herein by reference.

The drive housing 12 retains the various components of the disk drive10. The drive housing 12, illustrated in FIG. 1, includes a base 24 andfour (4) side walls 26. A typical drive housing 12 also includes a cover(not shown) which is spaced apart from the base 24 by the side walls 26.The drive housing 12 is typically installed in the case of a computer(not shown) or a word processor (not shown).

The disk assembly 14 includes one or more storage disks 28 which storedata in a form that can be subsequently retrieved if necessary. Magneticstorage disks 28 are commonly used to store data in digital form.Alternately, for example, each storage disk 28 can be optical ormagneto-optical. For conservation of space, each storage disk 28preferably includes a data storage surface 30 on each side of thestorage disk 28. These storage surfaces 30 are typically divided into aplurality of narrow annular regions (not shown) of different radii,commonly referred to as “tracks.” The storage disks 28 are manufacturedby ways known to those skilled in the art.

Depending upon the design of the disk drive 10, any number of storagedisks 28 can be used with the disk drive 10. For example, the disk drive28 can include one (1), two (2), three (3), six (6), nine (9), or twelve(12) storage disks 14. For two-sided storage disks 28, the disks 28 arespaced apart a sufficient distance so that at least one (1) transducerassembly 20 can be positioned proximate each of the storage surfaces 30of adjacent storage disks 28. To conserve space, a centerline (notshown) of consecutive disks 28 is typically spaced apart between aboutone millimeter (1.0 mm) to three millimeters (3.0 mm).

The storage disks 28 are spaced apart on a disk spindle 34 which ismounted to a spindle shaft (not shown) which is secured to the base 24.The disk spindle 34 rotates on a disk axis (not shown) relative to thespindle shaft on a spindle bearing assembly (not shown). Typically, thedisk spindle 34 and the storage disks 28 are rotated about the disk axisat a predetermined angular velocity by a spindle motor (not shown).

The rotation rate of the storage disks 28 varies according to the designof the disk drive 10. Presently, disk drives 10 utilize disks 28 rotatedat an angular velocity of between about 4,500 RPM to 10,000 RPM. It isanticipated that technological advances will allow for disk drives 10having storage disks 28 which rotate at higher speeds, such as about15,000 or more RPM.

The design of the E-block 16 depends upon the design of the actuatormotor 22 and the design of the disk drive 10. The actuator motor 22 canbe implemented in a number of alternate ways known by those skilled inthe art. For example, the actuator motor 22 can be a rotary voice coilactuator or a linear voice coil actuator. In the embodiment shown inFIG. 3, the actuator motor 22 is a rotary voice coil actuator. In thisembodiment, activation of the actuator motor 22 rotates the E-block 16and precisely moves the transducer assemblies 20 relative to the storagedisks 28.

As illustrated in FIG. 3, the actuator motor 22 includes a coil 36 thatis attached to the E-block 16. The coil 36 is disposed between a pair ofspaced apart permanent magnets 38 (only one (1) magnet 38 is shown) anda pair of spaced apart flux return plates 40 (only one (1) flux returnplate 40 is shown) which are secured to the drive housing 12.

The magnets 38 have pole faces of opposite polarity directly facingopposite legs of the coil 36. The resultant magnetic fields are suchthat current passing through the coil 36 in one (1) direction causesrotation of the E-block 16 in one (1) radial direction relative to thedisk assembly 14, while reverse current causes reverse directionmovement. Thus, the actuator motor 22 is able to bi-directionally rotatethe E-block 16 relative to the drive housing 12.

The transducer assemblies 20 transfer or transmit information betweenthe computer (not shown) or word processor (not shown) and the storagedisks 28. In the embodiment provided herein, each transducer assembly 20includes a load beam 42, a baseplate (not shown) securing the load beam42 to the actuator arm 18, a flexure 44, and a data transducer 46. Theload beam 42 attaches the flexure 44 and the data transducer 46 to theE-block 16. Typically, each load beam 42 is flexible in a directionperpendicular to the storage disk 28 and acts as a spring for supportingthe data transducer 46.

Each flexure 44 is used to attach one (1) of the data transducers 46 toone (1) of the load beams 42. Typically, each flexure 44 includes aplurality of conductive flexure traces 47 which are electricallyconnected to the data transducer 46. Each flexure 44 is subsequentlyattached to a flex circuit 48 which electrically connects the flexures44 to the disk drive 10.

Each data transducer 46 interacts with one (1) of the storage disks 28to access or transfer information to the storage disk 28. For a magneticstorage disk 28, the data transducer 46 is commonly referred to as aread/write head. It is anticipated that the present device can beutilized for data transducers 46 other than read/write heads for amagnetic storage disk 28.

The E-block 16 retains and positions the transducer assemblies 20proximate the appropriate track on the storage disk 28. As can best beseen with reference to FIGS. 4-9, the E-block 16 includes an actuatorhub 50 and a plurality of parallel actuator arms 18 which are attachedto and cantilever from the actuator hub 50. In the embodimentillustrated in the Figures, the actuator hub 50 is substantially tubularand can be mounted to an actuator shaft 52 (illustrated in FIG. 3). Theactuator hub 50 rotates on a hub axis 53 relative to the actuator shaft52 on an actuator bearing assembly (not shown).

The actuator arms 18 move with the actuator hub 50 and position thetransducer assemblies 20 between the storage disks 28, proximate thestorage surfaces 30. Each actuator arm 18 includes a proximal section 54which is secured to the actuator hub 50 and a distal section 56 whichcantilevers away from the actuator hub 50. The spacing of the actuatorarms 18 varies according to the spacing of the storage disks 28. Thedistance between consecutive actuator arms 18 is typically between aboutone millimeter (1 mm) to three millimeters (3 mm).

The distal section 56 of each actuator arm 18 can have a substantiallyrectangular cross-section and include a transducer hole 58 to facilitateattaching the transducer assemblies 20 to the actuator arms 18. As canbest be seen in FIGS. 4, 6, and 8, a width of each actuator arm 18 cantaper from the proximal section 54 to the distal section 56. The amountof taper can vary according to the design of actuator hub 50 and thedesign of the disk drive 10. Typically, the width tapers between abouteight degrees to twenty degrees (8°-20°).

Additionally, each actuator arm 18 can include one (1) or more armapertures 59 to lighten each actuator arm 18. The size, shape, andnumber of the arm apertures 59 must be consistent with the need for eachactuator arm 18 to be sufficiently rigid and the need to minimizeaerodynamic drag and turbulence.

FIGS. 4, 6, and 8, illustrate a perspective view of three alternateembodiments of an E-block 16. In each of these embodiments, the E-block16 includes four spaced apart actuator arms 18. For convenience, the topactuator arm 18 shall be designated the first actuator arm 18A, the nextactuator arm 18 shall be designated the second actuator arm 18B, thenext actuator arm 18 shall be designated the third actuator arm 18C,while the lowest actuator arm 18 shall be designated the fourth actuatorarm 18D.

In each embodiment illustrated in FIGS. 4, 6, and 8, the E-block 16includes one or more depopulated actuator arms 60. Each depopulatedactuator arm 60 is designed to retain less than two transducerassemblies 20. Two types of depopulated actuator arms 60 areillustrated, namely a single head actuator arm 62 and a no head actuatorarm 64. Importantly, each depopulated actuator arm 60 includes one ormore weighted segments 65 integrally formed into the depopulatedactuator arm 60 to improve the resonance characteristics of the E-block16. Because each weighted segment 65 is integrally formed into theE-block, the imaginary boundary of each weighted segment 65 isrepresented by dashed lines in FIGS. 5, 7, and 9.

The single head actuator arm 62 is designed to retain only onetransducer assembly 18 and includes a coupled side 66 and an uncoupledside 68. The transducer assembly 20 is attached to the coupled side 66while the uncoupled side 68 is barren and designed to not retain atransducer assembly. For each single head actuator arm 62 illustrated,the weighted segment 65 is integrally formed into the single headactuator arm 62 near the uncoupled side 68 and the distal section 56.

The weighted segment 65 of each single head actuator arm 62 is sized,shaped and located to improve the resonance characteristics of thesingle head actuator arm 62. For example, the weighted segment 65 of thesingle head actuator arm 62 can be designed to simulate a secondtransducer assembly (not shown) secured to the uncoupled side 68 of thesingle head actuator arm 62. Stated another way, the weighted segment 65is sized, shaped and located to counterbalance the one transducerassembly 20 secured to the coupled side 66 of the single head actuatorarm 62. Accordingly, the size, shape and location of the weightedsegment 65 is varied according to the design of the transducer assembly20.

The no head actuator arm 64 is designed to retain no transducerassemblies 18. Each no head actuator arm 64 includes a pair of opposeduncoupled sides 68 which are barren and a pair of spaced apart weightedsegments 65. Each weighted segment 65 is integrally formed into the nohead actuator arm 64 near one of the uncoupled sides 68 and the distalsection 56. Each weighted segment 65 is sized, shaped and positioned toimprove the resonance characteristics of the E-block 16. For example,the weighted segments 65 of the no head actuator arm 64 can be sized,shaped and located to simulate a pair of transducer assemblies (notshown) secured to the no head actuator arm 64. Accordingly, the size,shape and location of each weighted segment 52 is varied according tothe design of the transducer assemblies 20 used for the disk drive 10.

Importantly, the weighted segment 65 of the single head actuator arm 62compensates for the asymmetry caused by having only one transducerassembly 20 secured to the single head actuator arm 62. Somewhatsimilarly, the weighted segments 65 of the no head actuator arm 64compensate for the asymmetry, relative to the other actuator arms 18 onthe E-block 16, caused by having no transducer assemblies secured to theno head actuator arm 64. Thus, with the integrally formed weightedsegment(s) 65, the present invention compensates for the asymmetrywithout adding a separate component (not shown) which cantilevers awayfrom the actuator arm 18.

Preferably, the weighted segment 65 of the single head actuator arm 62is sized, shaped and positioned substantially similar to each weightedsegment 65 of the no head actuator arm 64. This allows the single headactuator arm 62 to have similar resonance characteristics as the no headactuator arm 64.

The specific design of each weight segment 65 is varied according to thedesign of the disk drive 10 and the transducer assemblies 20. Thespecific details of one embodiment of the weighted segment 65 canprobably best be understood with reference to FIGS. 4 and 5. Eachactuator arm 18 has an arm length 70 from the hub axis 53, a proximalsection thickness 72 proximal to the weighted segment 65 and an armlongitudinal axis 74. As illustrated in the FIG. 5, each weightedsegment 65 is positioned a segment distance 76 from the hub axis 53 ofthe actuator hub 50 and extends a segment length 78. Further, eachweighted segment 65 has a segment thickness 80. In the embodimentillustrated in FIG. 5, for each weighted segment 65, the segmentdistance 76 is approximately 25 mm from the hub axis 53 and the segmentlength 78 is approximately 2 mm, and the segment thickness 80 isapproximately 0.6 mm. Further, each weighted segment 65 weighsapproximately 0.07 grams. The specific size, shape and location of theweighted segments 65 can be precisely adjusted and optimized usingfinite element analysis.

Additionally, as illustrated in FIGS. 6-9, the E-block 16 can alsoinclude one or more double head actuator arms 84. Each double headactuator arm 84 includes a pair of coupled sides 66 and secures twotransducer assemblies 20. Because each double head actuator arm 84secures two transducer assemblies 20, each double head actuator arm 84is symmetrical and does not include a weighted segment 65. The doublehead actuator arms 84 are also referred to as being “populated”.

In addition to one or more weighted segments 65, each depopulatedactuator arm 60 has a lower lateral stiffness and lower resonancefrequency than each double head actuator arm 84. Further, each no headactuator arm 64 has a lower lateral stiffness and lower resonancefrequency than each single head actuator arm 62. Similarly, each singlehead actuator arm 62 has a lower lateral stiffness and lower resonancefrequency than each double head actuator arm 84. The lower lateralstiffness is believed to compensate for the fact that each weightedsegment(s) 65 does not cantilever like the transducer assembly 20.

The amount of reduced stiffness for each depopulated actuator arm 60varies according to the design of the disk drive 10, the transducerassembly 20 and the weighted segment(s) 65. The desired amount ofdifference in lateral stiffness can be precisely optimized using finiteelement analysis.

The lower lateral stiffness in the depopulated actuator arms 60 can beaccomplished in a number of ways. For example, the arm apertures 59 inthe depopulated actuator arms 60 can be larger than the arm apertures 59in the double head actuator arms 84. Alternately, the arm thickness 72for the depopulated actuator arms 60 could be less than the armthickness 72 for the double head actuator arms 84. In particular, in theembodiments provided herein, the arm thickness 72 for the no headactuator arm 64 is between approximately 0.1 to 0.2 millimeters lessthan the arm thickness 72 for the single head actuator arm 62.Similarly, the arm thickness 72 for the single head actuator arm 62 isbetween approximately 0.1 to 0.2 millimeters less than the arm thickness72 for the double head actuator arm 84.

Importantly, the present invention utilizes integrally formed weightedsegment(s) 65 and reduced lateral stiffness to modify the resonancecharacteristics of the no head actuator arms 64 and single head actuatorarms 62. Preferably, the resonance characteristics of each no headactuator arm 64 and single head actuator arm 62 are modified to simulateand have similar vibration characteristics as the double head actuatorarms 84. This allows the manufacturer of the disk drive 10 to bettertune all of the actuator arms 18 of the disk drive 10 to minimize datatransducer 46 slap and off-track motion. This decreases drive fragilityduring shipping, handling, installation and usage of the disk drive 10.

In summary, the lateral stiffness and the mass of the weightedsegment(s) 65 are increased until the natural resonance frequency of thearm modes on each depopulated actuator arm 60 align with the resonancefrequency of each populated arm 84.

FIG. 10 illustrates a computer simulation of the resonance curves foreach of the six data transducers 46 illustrated in FIGS. 8 and 9 aftermovement by the actuator motor 22. From FIG. 10, it is important torecognize that the resonance curves for each of the data transducers 46are substantially the same as a result of the unique design of theE-block 16.

FIG. 11 illustrates a computer simulation of G's to unload as a functionof shock duration for the embodiment illustrated in FIGS. 8 and 9. Morespecifically, FIG. 11 illustrates the G's required to lift thetransducer assembly 20 from the storage disk 28. In particular, thecurve designated 86 illustrates the movement of the transducer assembly20 for a single head actuator arm 62. Somewhat similarly, curvesdesignated 88 each illustrate the movement of one of the transducerassemblies 20 for the double head actuator arm 84. From FIG. 11, it isclear that as a result of the unique invention, the movement of thetransducer assemblies 20 is very similar when subjected to a shock.Thus, the manufacturer can better tune the disk drive 10 to minimize theeffects of a shock.

FIG. 12 illustrates a computer simulation of the deflection of theactuator arms 18 of the E-block 16 illustrated in FIGS. 8 and 9 as afunction of shock duration. In particular, curve designated 90illustrates the movement of the no head actuator arm 64, curvedesignated 92 illustrates the deflection of the single head actuator arm62, and curve designated 94 illustrates the movement of the double headactuator arm 84 for a given shock. As a result of the present invention,the actuator arms 18 react somewhat similarly when subjected to a givenshock. This allows a manufacturer to better tune the disk drive 10 tocompensate for such shocks.

Referring back to FIGS. 4 and 5, the E-block 16 illustrated therein isdesigned for use with a disk drive 10 having a single storage disk 28(not shown in FIGS. 4 and 5). The E-block 16 includes a pair of no headactuator arms 64 and a pair of single head actuator arms 62. In thisembodiment, the first and second actuator arms 18A, 18B, are no headactuator arms 64 while the third and fourth actuator arms 18C, 18D, aresingle head actuator arms 62. The one storage disk is positioned betweenthe two single head actuator arms 62.

In the embodiment illustrated in FIGS. 6 and 7, the E-block 16 isdesigned for use with a disk drive 10 having two storage disks 28 (notshown in FIGS. 6 and 7). In this embodiment, the first actuator arm 18Ais no head actuator arm 64, the second and fourth actuator arms 18B and18D, are single head actuator arms 62 and the third actuator arm 18C isa double head actuator arm 84.

In the embodiment illustrated in FIGS. 8 and 9, the E-block 16 isdesigned for use with a disk drive 10 having three storage disks 28 (notshown in FIGS. 8 and 9). In this embodiment, the first and fourthactuator arms 18A, 18D, are single head actuator arms 62 while thesecond and third actuator arms 18B, 18C, are double head actuator arms.

Many processes can be used to make the E-block 16. For example, theE-block 16 could be extruded and machined to the proper dimensions.Alternately, the E-block 16 could be injection molded or cast. Suitablematerials for the E-block 16 are an aluminum alloy, a magnesium alloy,reinforced plastic, or a ceramic material. Alternately, the actuatorarms 18 may be formed as separate pieces which are attached together bysuitable joining techniques known by those skilled in the art.

Uniquely, the present invention allows the E-block 16 for the alternateembodiments illustrated in FIGS. 4, 6, and 8, to each machined from thesame style of casting. Stated another way, the same mold (not shown) canbe used for the alternate embodiments illustrated in FIGS. 4, 6 and 8.After, the rough E-block (not shown) is removed from the mold, theactuator arms 18 are machined to the desired configurations. Thus, asingle mold can be used to make balanced E-blocks for alternate driveconfigurations. Further, because each weighted segment 65 is integrallyformed as part of the actuator arm 18, there are no additionalcomponents necessary.

Moreover, the weighted segment(s) 65 and the reduced lateral stiffnessallow the no head actuator arm 64 and the single head actuator arm 62 tohave similar vibration characteristics as the double head actuator arm84. Thus, the three embodiments of the E-block 16 illustrated in FIGS.4, 6, and 8, have somewhat similar vibration characteristics even thougheach is designed for an alternate drive configuration.

In summary, because of the unique process provided herein, the E-block16 for a number of alternate disk drives 10 can be made from the samemold. Further, the E-block 16 improves the resonance characteristics ofthe disk drive 10 without adding additional counterbalance parts and/orcomponents. Moreover, because each weighted segment 65 does notcantilever away from the actuator arm 18, the inertia of the E-block isnot significantly increased.

While the particular E-block 16 and disk drive 10 as herein shown anddisclosed in detail is fully capable of obtaining the objects andproviding the advantages herein before stated, it is to be understoodthat it is merely illustrative of the presently preferred embodiments ofthe invention and that no limitations are intended to the details ofconstruction or design herein shown other than as described in theappended claims.

What is claimed is:
 1. An E-block for a disk drive, the disk driveincluding one or more transducer assemblies and one or more storagedisks, the E-block comprising: an actuator hub; a single head actuatorarm secured to the actuator hub, the single head actuator arm includinga first uncoupled side, a coupled side substantially opposite theuncoupled side, and a first weighted segment integrally formed into thesingle head actuator arm near the first uncoupled side, the single headactuator arm being adapted to secure one transducer assembly to thecoupled side, the first weighted segment being sized, shaped and locatedto improve the resonance characteristics of the single head actuatorarm; and a no head actuator arm secured to the actuator hub, the no headactuator arm being designed to secure no transducer assemblies, the nohead actuator arm including a first uncoupled side, an opposed seconduncoupled side and a pair of spaced apart weighted segments, eachweighted segment being integrally formed into the no head actuator armnear one of the uncoupled sides, each weighted segment being sized,shaped and positioned to improve the resonance characteristics of the nohead actuator arm.
 2. The E-block of claim 1 wherein the first weightedsegment is sized shaped and located to counterbalance the one transducerassembly.
 3. The E-block of claim 1 including a double head actuator armsecured to the actuator hub, the double head actuator arm being adaptedto secure two transducer assemblies, the double head actuator arm havinga higher lateral stiffness than the single head actuator arm.
 4. TheE-block of claim 1 wherein the single head actuator arm has a higherlateral stiffness than the no head actuator arm.
 5. The E-block of claim1 further comprising a second no head actuator arm that extends awayfrom the actuator hub, the no second head actuator arm being designed tosecure no transducer assemblies, the second no head actuator armincluding a first uncoupled side, an opposed second uncoupled side and apair of spaced apart weighted segments, each weighted segment beingintegrally formed into the second no head actuator arm near one of theuncoupled sides so that the resonance characteristics of the second nohead actuator arm are approximately equal to the resonancecharacteristics of the no head actuator arm.
 6. An E-block for a diskdrive, the disk drive including one or more transducer assemblies andone or more storage disks, the E-block comprising: an actuator hub; anda no head actuator arm secured to the actuator hub, the no head actuatorarm securing no transducer assemblies, the no head actuator armincluding a first uncoupled side, a second uncoupled side, a firstweighted segment integrally formed into the no head actuator arm nearthe first uncoupled side, a second weighted segment being integrallyformed into the no head actuator arm near the second uncoupled side, theweighted segments being sized, shaped and located to improve theresonance characteristics of the no head actuator arm.
 7. The E-block ofclaim 6 including a double head actuator arm secured to the actuatorhub, the double head actuator arm being adapted to secure two of thetransducer assemblies, the double head actuator arm having a higherlateral stiffness than the depopulated actuator arm.
 8. A disk driveincluding: a drive housing; one or more storage disks which are securedto and rotate relative to the drive housing; one or more transducerassemblies; and an E-block which moves the one or more transducerassemblies relative to the drive housing, the E-block including anactuator hub and a no head actuator arm secured to the actuator hub, theno head actuator arm retaining no transducer assemblies, the no headactuator arm including a first uncoupled side, a second uncoupled side,a first weighted segment integrally formed into the no head actuator armnear the first uncoupled side, a second weighted segment beingintegrally formed into the no head actuator arm near the seconduncoupled side, the weighted segments being sized, shaped and located toimprove the resonance characteristics of the no head actuator arm. 9.The disk drive of claim 8 wherein the E-block includes a double headactuator arm secured to the actuator hub, the double head actuator armbeing adapted to secure two of the transducer assemblies, the doublehead actuator arm having an arm thickness which is greater than an armthickness of the no head actuator arm.
 10. The disk drive of claim 8including a double head actuator arm secured to the actuator hub, thedouble head actuator arm being adapted to secure two transducerassemblies, the double head actuator arm having a higher lateralstiffness than the no head actuator arm.
 11. An E-block for a diskdrive, the disk drive including one or more transducer assemblies andone or more storage disks, the E-block comprising: an actuator hub; a nohead actuator arm that extends away from the actuator hub, the no headactuator arm including a first uncoupled side, a second uncoupled side,a first weighted segment integrally formed into the no head actuator armnear the first uncoupled side, a second weighted segment beingintegrally formed into the no head actuator arm near the seconduncoupled side, the weighted segments being sized, shaped and located toimprove the resonance characteristics of the no head actuator arm; and adouble head actuator arm that extends away from the actuator hub, thedouble head actuator arm being adapted to secure two transducerassemblies, the double head actuator arm having a higher lateralstiffness than the depopulated actuator arm.
 12. The E-block of claim 11wherein the double head actuator arm has an arm thickness which isgreater than an arm thickness of the depopulated actuator arm.
 13. AnE-block for a disk drive, the disk drive including one or moretransducer assemblies and a storage disk, the E-block comprising: anactuator hub; and a first actuator arm and an adjacent, second actuatorarm that each extend away from the actuator hub, each actuator armincluding a distal section having a distal section thickness, the firstactuator arm supporting two transducer assemblies, the second actuatorarm supporting one transducer assembly, the distal section of the secondactuator arm including a weighted segment that is integrally formed intothe second actuator arm, the weighted segment having a segmentthickness, wherein material has been removed from each actuator arm sothat the distal section thickness of the first actuator arm isapproximately equal to the distal section thickness of the secondactuator arm minus the segment thickness of the weighted segment.
 14. AnE-lock for a disk drive, the disk drive including one or more transducerassemblies and a storage disk, the E-block comprising: an actuator hub;and a first actuator arm and an adjacent, second actuator arm that eachextend away from the actuator hub, each actuator arm including a distalsection having a distal section thickness, the first actuator armsupporting two transducer assemblies, the second actuator arm supportingone transducer assembly, wherein the distal section of the secondactuator arm includes an integrally formed weighted segment having aweight, and wherein the first actuator arm has a weight that isapproximately equal to a weight of the second actuator arm reduced bythe weight of the weighted segment, and wherein material has beenremoved from each actuator arm so that the distal section thickness ofthe second actuator arm is greater than the distal section thickness ofthe first actuator arm.
 15. A disk drive including a storage disk andthe E-block of claim
 14. 16. An E-block for a disk drive, the disk driveincluding one or more transducer assemblies and a storage disk, theE-block comprising: an actuator hub; and a first actuator arm and anadjacent, second actuator arm that each extend away from the actuatorhub, each actuator arm including a distal section having a distalsection thickness, the first actuator arm supporting two transducerassemblies, the second actuator arm supporting one transducer assembly,wherein material has been removed from each actuator arm so that thedistal section thickness of the second actuator arm is greater than thedistal section thickness of the first actuator arm, and wherein thefirst actuator arm has a weight that is approximately equal to a weightof the second actuator arm reduced by a weight of one transducerassembly.
 17. A disk drive including a storage disk and the E-block ofclaim
 16. 18. An E-block for a disk drive, the disk drive including oneor more transducer assemblies and a storage disk, the E-blockcomprising: an actuator hub; and a first actuator arm and a secondactuator arm that each extend away from the actuator hub, each actuatorarm including a distal section having a distal section thickness, thefirst actuator arm supporting two transducer assemblies, the secondactuator arm supporting no transducer assemblies, wherein material hasbeen removed from each actuator arm so that the distal section thicknessof the second actuator arm is greater than the distal section thicknessof the first actuator arm, and wherein the distal section of the secondactuator arm includes two spaced apart weighted segments that areintegrally formed into the distal section of the second actuator arm,each weighted segment having a segment thickness, and wherein the distalsection thickness of the first actuator arm is approximately equal tothe distal section thickness of the second actuator arm minus two timesthe segment thickness of one of the weighted segments.
 19. The E-blockof claim 18 further comprising a third actuator arm that is positionedbetween the first actuator arm and the second actuator arm, the thirdactuator arm supporting one transducer assembly, the third actuator armincluding a distal section having a distal section thickness, whereinthe third actuator arm includes a weighted segment that is integrallyformed into the distal section of the third actuator arm, the weightedsegment having a segment thickness, and wherein the distal sectionthickness of the third actuator arm is approximately equal to the distalsection thickness of the second actuator arm reduced by the segmentthickness of one of the weighted segments of the second actuator arm.20. An E-block for a disk drive, the disk drive including one or moretransducer assemblies and a storage disk, the E-block comprising: anactuator hub; a first actuator arm that extends away from the actuatorhub, the first actuator arm being adapted to support less than twotransducer assemblies, the first actuator arm including a firstuncoupled side and a weighted segment that is integrally formed into thefirst uncoupled side, the weighted segment of the first actuator armbeing formed by a material removal operation; a spaced apart secondactuator arm that extends away from the actuator hub, the secondactuator arm being adapted to support at least one transducer assembly;and a third actuator arm that is adapted to support no transducerassemblies, and wherein the third actuator arm includes two weightedsegments that are integrally formed into the third actuator arm, thethird actuator arm being formed by a material removal operation; whereinthe first actuator arm has a weight that is greater than the weight ofthe second actuator arm; and wherein the first actuator arm and thesecond actuator arm have different resonance characteristics.
 21. AnE-block for a disk drive, the disk drive including one or moretransducer assemblies and a storage disk, the E-block comprising: anactuator hub; a first actuator arm that extends away from the actuatorhub, the first actuator arm having a proximal section adjacent to theactuator hub, the proximal section having a proximal section thickness,and a distal section having a distal section thickness, the distalsection thickness being greater than the proximal section thickness; anda spaced apart second actuator arm that extends away from the actuatorhub, the second actuator arm having a proximal section adjacent to theactuator hub, the proximal section having a proximal section thickness,and a distal section having a distal section thickness that is at leastas great as the proximal section thickness of the second actuator arm,but less than the distal section thickness of the first actuator arm.22. The E-block of claim 21 wherein the first actuator arm is adapted tosupport one transducer assembly and the second actuator arm is adaptedto support two transducer assemblies.
 23. The E-block of claim 21wherein the first actuator arm is adapted to support no transducerassemblies and the second actuator arm is adapted to support onetransducer assembly.
 24. A disk drive including a storage disk and theE-block of claim
 21. 25. An E-block for a disk drive, the disk driveincluding one or more transducer assemblies and a storage disk, theE-block comprising: an actuator hub; a first actuator arm that extendsaway from the actuator hub, the first actuator arm having a proximalsection near the actuator hub, the proximal section having a proximalsection thickness, and a distal section having a distal sectionthickness, the distal section thickness being greater than the proximalsection thickness; a spaced apart second actuator arm that extends awayfrom the actuator hub, the second actuator arm having a proximal sectionnear the actuator hub, the proximal section having a proximal sectionthickness, and a distal section having a distal section thickness thatis at least as great as the proximal section thickness of the secondactuator arm, but less than the distal section thickness of the firstactuator arm; and a spaced apart third actuator arm that extends awayfrom the actuator hub, the third actuator arm being positioned so thatthe second actuator arm is substantially between the first actuator armand the third actuator arm.
 26. The E-block of claim 25 wherein thethird actuator arm has a proximal section near the actuator hub, theproximal section having a proximal section thickness, and a distalsection having a distal section thickness that is at least as great asthe proximal section thickness of the third actuator arm, but less thanthe distal section thickness of the second actuator arm.
 27. The E-blockof claim 25 wherein the third actuator arm has a proximal section nearthe actuator hub, the proximal section having a proximal sectionthickness, and a distal section having a distal section thickness thatis at least as great as the proximal section thickness of the thirdactuator arm, but less than the distal section thickness of the secondactuator arm.
 28. The E-block of claim 25 wherein the first actuator armsupports no transducer assemblies, and the second actuator arm supportsonly one transducer assembly and the third actuator arm supports twotransducer assemblies.
 29. The E-block of claim 25 wherein the firstactuator arm supports one transducer assembly and the second actuatorarm supports two transducer assemblies.
 30. An E-block for a disk drive,the disk drive including one or more transducer assemblies and a storagedisk, the E-block comprising: an actuator hub; a first actuator arm thatextends away from the actuator hub; a second actuator arm that extendsaway from the actuator hub, the second actuator arm having a differentresonance characteristics than the first actuator arm; and a thirdactuator arm that extends away from the actuator hub, the third actuatorarm having different resonance characteristics than the first actuatorarm and the second actuator arm.
 31. The E-block of claim 30 wherein thefirst actuator arm is adapted to support no transducer assemblies, thesecond actuator arm is adapted to support one transducer assembly, andwherein the third actuator arm is adapted to support two transducerassemblies.
 32. The E-block of claim 30 further comprising a fourthactuator arm, wherein the second actuator arm and the third actuator armare positioned between the first actuator arm and the fourth actuatorarm.
 33. An E-block for a disk drive, the disk drive including one ormore transducer assemblies and a storage disk, the E-block comprising:an actuator hub; a first actuator arm that extends away from theactuator hub, the first actuator arm being adapted to support less thantwo transducer assemblies, the first actuator arm including (i) a distalsection with a distal section thickness, (ii) a first uncoupled side,and (iii) a weighted segment that is integrally formed into the firstuncoupled side, the weighted segment of the first actuator arm beingformed by a material removal operation; and a spaced apart secondactuator arm that extends away from the actuator hub, the secondactuator arm being adapted to support at least one transducer assembly,the second actuator arm having a distal section with a distal sectionthickness; wherein the first actuator arm has a weight that is greaterthan the weight of the second actuator arm, wherein the first actuatorarm and the second actuator arm have different resonancecharacteristics, and wherein the actuator arms are formed by removingmore mass from the distal section of the second actuator arm than fromthe distal section of the first actuator arm.
 34. A disk drive includinga storage disk and the E-block of claim
 33. 35. A disk drive comprising:a storage disk; and an E-block that includes (i) an actuator hub, (ii) ano head actuator arm that extends away from the actuator hub, the nohead actuator arm being adapted to retain no transducer assemblies, and(iii) a single head actuator arm that extends away from the actuatorhub, the single head actuator arm supporting a single transducerassembly, wherein the no head actuator arm and the single head actuatorarm have different resonance characteristics.
 36. The disk drive ofclaim 35 wherein the no head actuator arm includes a distal sectionhaving a distal section thickness, the no head actuator arm having twoweighted segments integrally formed into the distal section, eachweighted segment having a segment thickness, and wherein the single headactuator arm Includes a distal section having a distal sectionthickness, the distal section thickness of the single head actuator armbeing approximately equal to the distal section thickness of the no headactuator arm minus the segment thickness of one of the weightedsegments.
 37. The disk drive of claim 35 further comprising a doublehead actuator arm that extends away from the actuator hub, the doublehead actuator arm supporting two transducer assemblies.